U.S. lawmakers are expressing concern over the mounting drug-related violence in Mexico and the spillover into the United States.  At Congressional hearings on Tuesday, lawmakers urged the Obama administration to step up efforts to help Mexico crush the drug cartels that are the source of the violence.

The attacks on police and killings have spiraled out of control, especially in Mexican cities along the U.S. border such as Juarez.

Mexican President Felipe Calderon in recent weeks has deployed massive numbers of troops to stem the violence.  

At a House subcommittee hearing Tuesday, the State Department's top official for Latin America, Thomas Shannon, praised Mr. Calderon and urged Congress to continue helping Mexico. 

"He needs to show success on the ground, he needs to show that the kinds of steps he's taking now are going to allow Mexicans to recapture their communities," Shannon said. "And this is why it is so important for us to engage as quickly and decisively as we can."

Mexico is receiving U.S. funds for training, equipment and other initiatives under the Merida Agreement.  Signed last year during the Bush administration, the agreement is aimed at fostering closer cooperation between the United States, Mexico and Central America to combat the drug trade.

At a different House hearing, U.S. officials testified about joint efforts to stop drug smuggling.   

But some lawmakers complained that Washington is not doing enough. 

"You can only imagine what would happen if the gangs took over Mexico, the government of Mexico, it's not beyond comprehension," Republican Congressman Harold Rogers said. "And the difficulties that would cause the United States are unimaginable, and yet I do not see the US taking this thing as serious as they need to take it."

The delay in delivering US-made helicopters to Mexico under the Merida Agreement was a special point of contention at the hearings.  

But David Johnson, the State Department's head of Narcotics and Law Enforcement, downplayed the concerns. 

"While they certainly don't have the capability they think they need and we think they need to succeed ultimately, they do have some capability and they are using it," Johnson said.

More than 6,000 people were killed in Mexico's drug wars last year, and so far this year the violence has only increased.